Log unification of VCS agent's entry points

Earlier, the logs of VCS agents implemented using script and C/C++ language were scattered between the engine log file and agent log file respectively.

The logging is improved so that logs of all the entry points will be logged in respective agent log file. For example, the logs of Mount agent can be found in the Mount agent log file located under /var/VRTSvcs/log directory.

Moreover, using LogViaHalog attribute, user can switch back to the older logging behavior. This attribute supports two values 0 and 1. By default the value is 0, which means the agent's log will go into their respective agent log file. If value is set to 1, then the C/C++ entry point's logs will go into the agent log file and the script entry point's logs will go into the engine log file using halog command.

Note:

Irrespective of the value of LogViaHalog, the script entry point's logs that are executed in the container will go into the engine log file.